A tidal marsh is a type of marsh that is found along rivers, coasts and estuaries of which the flooding characteristics are determined by the tidal movement of the adjacent estuary, sea or ocean. Tidal wetlands experience many overlapping persistent cycles, including day - night temperature fluctuations, diurnal tides, semi-diurnal tides, spring -neap tides, seasonal vegetation growth and decay, decadal El Niño-Southern Oscillation climate variations, and centennial to millennial trends in sea level and climate. They are also impacted by transient disturbances such as hurricanes, floods, storms, and upland fires.
According to the salinity of the flooding water, tidal marshes are differentiated into freshwater, brackish and saline varieties. They may also be classified into coastal marshes and estuarine marshes on the basis of their landscape position. From landscape position one can infer a lot about the origin, controlling processes, age, disturbance regime, and future of a tidal marsh. Tidal freshwater marshes are further divided into deltaic and fringing types. Extensive research has been conducted on deltaic tidal freshwater marshes in Chesapeake Bay, which saw many form as a result of historic deforestation and intensive agriculture.
Internally, individual marshes of each salinity level are commonly zoned into lower marshes (also called intertidal marshes) and upper or high marshes, based on their elevation with respect to the sea level. In tidal freshwater marshes there can also be a middle marsh zone.
